Occasionally functions as a noun referring to someone/something in third position or a third-class degree in UK universities.
The 3rd to arrive should lock the door.
Le troisième à arriver doit fermer la porte à clé.
mention passableUniquement au sens universitaire britannique. Used to denote the ordinal number three in numeric form.
She finished 3rd in the race.
Elle a terminé troisième de la course.